Electric circuit breakers



Dec. 17, 1957 A. c. GlBsoNyETAL 2,816,974

ELECTRIC CIRCUIT BREAKERS Inventors:

Arthur C. Gibson, Dou'ghas Wgld,

H i I 'I @j Devc. 17,1957

Filed )lay 17, 1955 A. c. GIBSON lawu.l 2,816,974

ELECTRIC CIRCUIT BREAKERS :s sheds-sheet' 2 Figa 0 Inventors:

Douglas Wgld,

bg M/m/ The. Attorney.

Dec. 17, 1957 A. c. GIBSON ETAL 2,816,974

ELECTRIC CIRCUIT BREAKERS Filed may 1v, 1955 s sheets-sheet s Inventors:

Ari-hush C. Gibson, Douglas Wgld,

b5 {wifi/aw Thel Attorneg.

United States Patent O ELECTRIC CIRCUIT BREAKERS Arthur Charles Gibson, London, and Douglas Wyld, Middlesex, England, assignors to The British Thomson- Houston Company Limited, London, England, a British company Application May 17, 1955, Serial No. 509,046

Claims priority, application Great Britain May 21, 1954 14 Claims. (Cl. 20G-89) This invention relates to electrical circuit breakers of the kind wherein the contacts are biased to the closed position and are operable to the open position by a solenoid or other operating means energized by the circuit breaker current whereby in response to said current exceeding a predetermined value said operating means will open the contacts so as to interrupt the current, the contacts then reclosing and being again opened if the cir-- cuit conditions are still such that the current exceeds said value. Counting means are provided whereby after a predetennined number of opening and closing operations have been performed in response to such circuit conditions, the contacts are finally maintained in the open position. Timing mechanism may be arranged so that the successive time periods for which the contacts are open and closed before being finally locked open follow1 a predetermined schedule. Circuit breakers of the kind referred to are, for example, well adapted for use in rural electrication schemes and other remote locations wherein fault conditions may normally be cleared either in themselves or as a result of fuses included in the circuits.

The present invention has for its object to provide advantageous operating mechanism in circuit breakers of the kind referred to.

In circuit breakers of the kind referred to, the time periods for which the contacts remain closed, both after the initial occurrence of the predermined over-current conditions and during each subsequent period for which the contacts remain closed as a result of a sequence of opening and closing operations in response to a given occurrence of over-current conditions, is determined by means of a dashpot or other time delay device coupled with the mechanism by which the solenoid or other device operates the contacts. The movement of the mechanism is therefore comparatively slow and the invention has for its object to provide convenient and advantageous mechanism whereby the comparatively slow movement derived from the solenoid or other device will result in rapid contact movement at the desired time.

According to the present invention, in an electric circuit breaker of the kind referred to, the operating mechanism comprises a toggle and an operating spring connected with said toggle so as to tend to collapse the latter, one link of said toggle being connected with the solenoid or other device and the other link of said toggle being connected with the moving contact, or switch member, of the circuit breaker and being a floating link, that is to say, having its end remote from the connection with the rst said link arranged for movement in the plane of action of the toggle. Said free end of the second toggle link co-operates with abutment means arranged so that said abutment lies in the path of movement of the free end of the toggle when the links of the latter are in line with one another. In the closed position of said moving contact, or switch member the toggle is over-centre with respect to said spring so that the connection between the two links of the toggle will, upon operation of the solenoid or other device, be moved toward the line of action of the spring, a corresponding movement of the second-mentioned toggle link then being in the direction to maintain the contacts closed. The movement of the toggle by the solenoid or other device thus tends to straighten the links with respect to one another and brings the free end of the second link into engagement with said abutment. Continued movement of the solenoid moves the toggle over-center with respect to the spring, but said abutment prevents the spring causing collapse of the toggle until the latter has been moved so far over-center that the free end of the second link is withdrawn laterally from said abutment whereupon the operating spring is permitted rapidly to collapse the toggle and thereby open the contacts. It will be seen that at the time the toggle is withdrawn from the abutment, the contact pressure is suddenly released and the energy stored in the operating spring by extension of the toggle linkage by the solenoid is then released to cause rapid movement of the moving contact. An abutment will also normally be arranged in cooperation with the free end of the second-mentioned toggle link for providing corresponding operation in the closing direction of the circuit breaker.

The invention comprises further features, specific embodiments of which are included in one arrangement of circuit breaker now to be described by way of example with reference to the accompanying drawings.

In the drawings:

Fig. l is a vertical cross-sectional elevation of the circuit breaker;

Fig. 2 is an enlarged cross-sectional view taken along the line II-II of Fig. l;

Fig. 3 is a detailed view of a portion of the mechanism shown in Fig. l, the position of the parts being illustrated at diiferent intervals during a breaker opening stroke;

Fig. 4 is a vertical cross-sectional elevation of the circuit breaker taken on the line IV-IV of Fig. l;

Fig. 5 is a sectional plan view taken on the line V-V of Figs. l and 2; and

Fig. 6 is a vertical cross-sectional view of a preferred arrangement of dashpot employed in the circuit breaker of Figs. 1-5. This View is taken looking in a direction opposite to that shown in Fig. 1.

This circuit breaker comprises a xed circuit breaker head casting 1 supporting a depending oil tank 2, in which the circuit breaker parts and operating mechanism hereinafter to be described are located. A pair of insulating bushings 3 and 4 extend through the head 1 and support therein conductors 5 and 6 which form terminals for connection with the line conductors and at their lower ends are connected in a manner hereinafter to be described.

The contacts and operating mechanism are mainly supported from a main framework comprising four vertical rods 7, 8, 9, and 10' which at their upper ends are secured to the head casting 1such as by means of frame plates 20 and 21. The contact arrangement comprises a moving contact, or switch member, 11, of elongated rodlike form which cooperates with a iixed contact (not shown) mounted within an explosion pot or other arc control structure of any suitable type indicated generally at 12. In the example being described, the contacts are of butt type. The fixed contact and arc control device are mounted on a conductive casting 13 which is bolted to the frame rods 7 and 8. The moving contact is guided by means of a cross bar 14 of insulating material, supported from the frame rods 7 and S and provided with a vertical bore through which the rod 11 freely extends.

At its upper end the contact rod 11 is connected by means of a flexible strap conductor l5 and a conducting 3 member 16 with the terminal stem within the bushing 4. The flexible conductor l5 thus allows vertical movement of the rod lll from the illustrated closed position upwardly to the open position.

The contact rod ll is connected at its upper end with a vertical insulating lift rod 17, the upper end of which is connected with a straight-line operating linkage comprising a link 1S pivotally mounted on a fixed pivot i9 supported in frame plates 2i? and 2 depending from the upper ends of the frame rods 7-10, and a switch lever 22 which at one end is pivotally connected, namely at 23, with the upper end of the insulating rod i7, and at an intermediate point, namely 21.1 is pivotally connected with the link i3. The right-hand end of the lever 22 in Fig. l is pivotally connected at 25 with a swinging link pivotally mounted on a fixed pivot 27. The arrangement is thus such that angular motion imparted to the lever 22 by means of an operating link 2% will result in the lever 22 pivoting about the pin 25 but so that the pin 2d will be constrained to move in an arcuate path about the xed pin i9 as a center, and the pin 23 therefore moves substantially in a vertical straight line.

The link has pivotal connection at its lower end with a toggle linkage comprising links 29 and 30, the link 3) being mounted on a fixed pivot at 3l supported by the frame plates 2d and 2l. The link 30 includes a tail portion 32 extending past the pin 3l for a purpose hereinafter to be described. A tension spring 33 extends between the pins 2da and 3l thereby tending to collapse the toggle.

The opening of the switch contacts is effected, in a manner which will hereinafter appear, by means of a solenoid 34 carried by the main framework, and having a plunger 3S connected by a connecting link 3o with a lever 37 pivoted at 3d in frame plates secured to the frame rods 8 and 9, one of said frame plates appearing at 39. At its free end the lever 37 has a pivotal connection at dil with a link di, the upper end of which has pivotal connection at t2 with the toggle link 3d.

The solenoid plunger 353 and with it the lever 37 and toggle link 3d are biased upwardly to the illustrated position by means of a compression spring 43 acting between an abutment ldlon the link 3o and a fixed abutment d5 mounted between the frame plates of which one is shown at 39. rl`he solenoid has its winding connected in series between the casting 13, carrying the fixed Contact, and the terminal stem within the bushing 3.

A latch or detent member 43 is mounted on a fixed pivot 49 and biased by means of a compression spring 5@ engaging the lower end of the latch and urging the latter toward the right-hand in Fig. l. A `suitable stop a is provided for limiting such movement of the latch or detent d to the illustrated position. As may be seen in Fig. 4, the latch 43 has a notch in its upper surface which functions in a manner soon to be described.

The arrangement includes means for accelerating the contact-opening action as will now be described by referring especially to Figs. l and 2. The tail end 32 of the toggle link 3d carries a pin il which works in a slot 52 in a link 53 which is pivoted at 54 in a manner hereinafter to be described. The pin 5l extends also through a slot 55 in a member 56 which comprises also a rod 57 extending at its upper end through an opening in the end of a lever 5S which is mounted on a fixed pivot 59. A compression spring o@ surrounding the rod 57 bears at its end on the upper surface of the member 56 and the under surface ot' the said end of the lever The upper end of the rod S7 is screw-threaded and carries a nut or abutment member engaging with the upper surface of the lever so as to limit the downward movement of the rod with respect to said lever. The lever has pin and slot connection at nl with a lever o2 mounted on a fixed pivot 63, said lever 62 including a heel part 64 which is adapted to engage beneath the a pin 24 so that clockwise movement of the lever 62 in Fig. 1 will urge the lever 22 upwardly.

As seen in Fig. l, a dashpot 65 is mounted on the main frame and the piston of this dashpot is connected by means of its piston rod 66 and a link 67 with the pin itl whereby the dashpot piston is moved with the solenoid plunger 3S. Preferably, the link 67 includes a spring whereby the vibration of the solenoid plunger at the supply frequency will not be transmitted to the dashpot piston. The lower part of the dashpot is provided with a discharge valve 120, llZli' (Fig. 6) having an operating member 68 fixed to a shaft 69 and displaceable by a cam member 70 pivotally mounted on the fixed pivot 7l. The dashpot and discharge valve referred to are preferably arranged as hereinafter described with reference to Fig. 4. The cam member 7d is operable by means of a member 72 hereinafter referred to as the monitoring rack which is adapted for substantially vertical movement, said rack being located toward its lower end by means of a pin 73 secured to the dashpot and extending through a slot 7d in the rack, and the upper end of the monitoring rack having a pin connection 7S with a link 76 loosely mounted on the pivot The connection between the rack 72 and the cam member '7% comprises a link 77 having a pin connection at 7F,- with the lower end of the rack and a pin and slot connection 79 with said cam member.

As will be seen, the arrangement of the link 77 and pin and slot connection 79 is such that movement of the rack 72 upwardly will initially be without effect on the position of the member 7d but when the pin has risen sufficiently to take up the lost motion in the connection 79 further movement of the rack will result in the link 77 displacing the member 7d in the counter-clockwise ldirection in Fig. l.

The rack 72 is actuable by a pawl Sti pivotally mounted at 81 on the lever 37, this pawl having a catch portieri S2 co-operating with teeth d3 formed on the edge of the rack. The pawl d@ is biased by means of a hairpin spring Sil towards engagement with the rack, but is normally held clear of the rack by means of an adjustable stop SS which is mounted on the fixed framework and co-operates with a portion of the pawl so that in the illustrated position of the lever 37 said stop holds the catch S2 of the pawl out of engagement with the rack.

The rack 72 is also coupled by means of a lever 37 with a clockwork or other timing device S8 mounted on the framework and operative to delay the downward movement of the rack after the latter has been raised, this downward movement being due to the weight of thc rack. Since this timing device 83 may be of any suitable conventional form, it has been shown schematically only.

rEhe arrangement also includes lock-out controlling means in which the link 7 6, by which the upper end of the rack 72 is located, forms a toggle with a further link gd, said link 9i) having a pin connection at 9i with a lever 92 which is pivotally mounted on the pin The lower end of the lever 92 is normally clear of the tail 32 of the toggle link 36. The pin 5d is carried by a bell-crank lever 93 mounted on a fixed pivot carried in lateral extensions, one of which appears at 95 in Fig. l, of the frame-plates 2i) and 2l. The bell-crank 93 has a pin connection 96 with a re-entrant toggle comprising respective long and short links 97 and 93, the link 9S being loosely pivoted on the fixed pin 27, this pin serving also to limit the downward movement of the link 97 to the position in which it is illustrated. Tension springs 99 extend between the pin liti@ connecting the links i7 and 98 and fixed pins l l. in the illustrated position of the parts the line of action of this spring, which tends to draw the pins It@ and lill together, lies below the pin 27 so that the toggle and spring 99 are maintained in the illustrated set position, and the spring is without edect on the operation of the mechanism.

It will be convenient at this stage to describe the operation of the contacts by means of the solenoid. The contact being in the closed position, then upon the occurrence of a sufficient overload current the solenoid plunger is drawn downwardly against the force of the spring 43 so as, by means of the lever 37 and link 41, to actuate the toggle link 30 in the counter-clockwise direction in Fig. l about the pin 31. This movement of the link 3i) therefore causes outward movement of the pin 28L at the end of the other toggle link 29, by swinging of the lever 28 about the pin 24. This movement extends the spring 33 but is without effect on the lever 22 until the toggle links move over-center, that is to say, until the pivotal connection at 47 moves below the line joining the pins 28a and 31. Thereafter the toggle, having thus been moved over-center is permitted to collapse so that the spring 33 will cause clockwise movement of link 29 about pin 47 so as to lift the link 28 and thereby rotate the lever 22 about the pin 25 and thereby lift the lift rod 1'7 and contact rod, or switch member, 11 out of engagement with the xed contact.

As shown in Fig. 3, the collapsing of the links 29 and 30 in the manner above described is, however, positively controlled by means of the interfering abutment or latch 48, which interferes with collapse of the toggle 29, 30 until the solenoid has nearly completed its downward stroke. The position of the latch 48 is such that when the toggle links 29 and 30 are in line with one another, the outer end, left-hand in Fig. 3, of the link 29 will be located beneath the lower end of the latch 48. The dimensions of the various parts are such that the said end of the link 29 will remain under the lower end of the latch 48 also during continued downward movement of the pin 47 past toggle center, being only released from said latch by movement toward the right-hand in Fig. 3 when the solenoid has nearly completed its downward stroke. The dotted lines of Fig. 3 illustrate the fullyopen position of the toggle links 29 and 30 after release from the abutment or latch 48. The latch, or abutment, thus renders the toggle collapsing action ineffective to produce contact-opening movement of the operating lever 22 until the solenoid has nearly completed its stroke.

The latch, or abutment, 48 furthermore prevents movement of the operating lever 22 by the accelerating spring 60 until the solenoid has nearly completed its opening stroke since although the spring 60 has been stressed by the upward movements of the tail 32 of the toggle link 30 so that the lever 62 is therefore in engagement with the pin 24 and urging the latter upwardly, said pin 24 is prevented by the restrained link 28 from moving until the toggle link 29 clears the latch or abutment 48.

With this arrangement, the downward movement of the solenoid plunger, causing counter-clockwise movement in Fig. l of the toggle link 30 to lift the pin 51 will, after the lost motion provided by the slot 55 has been taken up, result in the member 56 being lifted by the pin 51, as will be evident from Fig. 2. The spring 60 is thus compressed against the lever 58 with the result that an upward force is applied against the pin 24 by the heel 64 of the lever 62. Accordingly, the spring 60 thus tends to open the contacts but is unable to move the pin 24 until the toggle link 29 is withdrawn from the latch or abutment 48 in the manner hereinbefore described. The link 29 is not so withdrawn from the latch or abutment until nearly the end of the downward stroke of the plunger 35. It will thus be seen that during the major part of the opening stroke of the solenoid, energy is stored in the spring 60 by progressive compression thereof, and this energy is released at the end of the opening stroke ofthe solenoid `so as to accelerate the opening movement of the contact rod 11. The slot 52 in the member 53 then allows the member 53 to move upwardly independently of the pin 51, as is required should the breaker be subsequently locked-open, as will soon appear.

In the open condition of the mechanism, the end of the toggle link 29 is positioned above the notched portion of t-he latch member 48. During reclosure, when the link 41 is moved upwardly by spring 43, the end of the link 29 moves into engagement with this notched portion and is thus retained against downward movement as the pin 47 moves above the line of action of the spring 33 until this upward movement of the pin 47 draws the end of link 28 (to the right hand in Fig. l) clear of the member 48, when the spring 33 is then permitted rapidly to collapse the toggle and by means of link 28 move the switch lever 22 rapidly downwardly. During reclosure the energy of the reclosing spring 43 in returning the plunger 35 to the normal position is thus stored in the toggle linkage until near the end of its reclosing stroke, by the initial extension of spring 33 as the toggle 29, 30 is moved toward center. Said energy is then released near the end of the closing stroke of the solenoid plunger to effect rapid re-engagement of the contacts.

in the operation of this arrangement the dashpot is operative to control the speed of the downward and upward strokes of the solenoid plunger 35 to open and close the circuit breaker. As will appear from the description hereinafter given of the dashpot the latter in the embodiment being described provides a Xed rate of upward, or reclosing, movement of the plunger but the rate of downward, or opening, movement of the piston is controlled by the discharge valve 120, 121 and therefore by the position of the valve operating lever 68. In the illlustrated position of said valve operating lever 68 the control valve is fully open so that the solenoid can move rapidly and therefore will open the contacts promptly in response to an over current. The downward movement of the lever 37 during the opening movements of the circuit breaker results in the catch surface 82 of the pawl 80 engaging beneath the uppermost tooth 83 on the rack. The circuit breaker having been opened the solenoid is consequently de-energized and the plunger 35 therefore moves upwardly by spring 43 to its original position. During this movement the pawl raises the monitoring rack but the latter in the embodiment being described is not effective during this part of its movement to displace the cam member 70. The circuit breaker having been re-closed, the solenoid is again energized and if the over-current conditions have persisted the plunger 35 will again be drawn downwardly so as for a second time to open the circuit breaker promptly. The consequent termination of current will again result in the circuit breaker re-closing and during the re-closing movement the pawl 80 having engaged the second of the teeth 83 will have lifted the rack 72 a corresponding further amount. This movement of the rack will be sufcient to displace the cam member 70 so as to close the control valve referred to of the dashpot. Assuming that the overcurrent conditions still persist, then the solenoid will again draw the plunger 35 downwardly but the speed of movement will now be retarded by the closure of said control valve in the dashpot. A corresponding period will therefore elapse before the contacts open, it being remembered that the operating mechanism is such that the contacts do not open until the solenoid plunger has nearly completed its downward movement.

If the over-current conditions are not cleared during this longer closed period of the circuit breaker, then when the contacts re-close the plunger will once more be drawn downwardly to re-open the contacts. The member 70 includes an arcuate surface 89 so that during the previous upward movement of the monitoring rack 72 the arm 68 remains in its displaced position. The contacts therefore remain closed for a similar period to that for which they were last closed.

If the over current conditions have not been cleared during the rst of the two longer periods of reclosure the 7 upward movement of the lever 37 results in the pawl 80, which has now engaged with the lowest of the teeth S3, lifting the rack to a position which by the means now to be described will result in locking out the circuit breaker.

The arrangement is such that when the rack 72 has been raised to its uppermost position, corresponding with the lever 37 being in its illustrated position with the pawl just disengaged from the lowermost of the teeth 03, then the toggle links 76, will have drawn the lower end of the lever 92 to the left hand in Fig. 1 into the path of movement of said tail part 32. The part 32 thus has engaged with the lower end of the lever 92 during the upward movement of said part 32 resulting from the downward movement of the solenoid plunger 35. This engagement occurs when the toggle links 29 and 30 are approaching the straight-line condition, that is to say, prior to the opening of the contacts. Continued movement of the link 30 by the solenoid plunger and further upward movement of the part 32 will therefore lift the link 92 which, as will now be described, has the result of locking the circuit breaker in the open position.

The manual operating mechanism comprises an operating lever 102 made fast to a shaft 103 and conveniently provided with a ring-shaped end 104 adapted to receive a hook on an operating pole. the shaft 103 is connected with the bell-crank 93 by means of a toggle linkage comprising links 106 and 107 pivoted together at 108 and connected with the lever 105 by a pin 109 and with the bell-crank by the pin 96. The pin lies above the line joining the pins 96 and 109 so that the toggle linkage will collapse to allow the hereinafter described clockwise movement of the bell-crank lever 93, the link 106 pivoting freely about the pin 109 during this movement with no ensuing movement of the manual handle 102.

The upward movement of the lever 92 as hereinbefore described by the part 32 of the toggle link 30, when the rack 72 is in its uppermost position, moves the bell-crank 93 in the clockwise direction in Fig. 1.

The line between the pivots 100 and 101 will now lie above the pivot 27 so that the movement of the bell-crank lever is enabled to cause movement of the links 97 and 98 tending to raise the pin 100. At the same time the pin 100 is moving upwardly so that the line of action of the spring 99 moves above the pivot 27 and will then cause rapid movement of the pin 100 in the clockwise direction and of the pin 96 also in the clockwise direction thereby continuing the clockwise vmovement of the bell-crank 93 to lift the slotted link 53. The engagement of the pin 51 with the bottom of the slot 52 in said link 53 then transmits the force of the spring 99 to the toggle link 30. rf'he spring 99 through the link 53 and the toggle lever 30 thus acts downwardly on the link 41 and is of such strength as to overcome the re-closing spring 43 so that the lever 30 is maintained in the position to which it is actuated in the open position of the circuit breaker. In other words, the toggle link 29 is maintained in the collapsed position wherein the spring 33 holds the switch lever 22 in its upper position and the contacts in the open position.

The cessation of current in the solenoid 3d therefore does not now result in re-closure of the circuit breaker. ln order to re-close the circuit breaker a manual operating member has to be actuated mechanically as will now be described.

in order to reset the circuit breaker, the end 10d of the operating lever is moved upwardly so as to rotate the lever in the clockwise direction and thereby to bring the toggle links 106 and 107 into the straight line position. A hairpin or other tension spring 100L is provided on the pin 10S and the end of the spring abuts on the links 106 and 107 so as to tend to maintain said links just over the set position of the toggle. ln other words the toggle linkage is now set so as to constitute an integral thrust-resistant structure. Return movement of the operating lever 102 and with it of the lever 105 will therefore transmit the A lever 105 made fast to L counterclockwise movement of pin 109 to the bell-crank so as to return the latter to the illustrated position. The slotted link 53 then releases the toggle link 30 so that the spring 43 will now cause the solenoid plunger 35 to lift and so reclose the circuit breaker.

A fixed abutment 110 cO-operates with the link 106 so as to break the toggle 106, 107 during the nal part of the return movement of the lever 102, whereby the lockout mechanism is in condition for subsequent operation. Thus, the circuit breaker is trip-free since the collapse of the toggle 106, 107 effectively disconnects the operating handle 102 from the bell-crank 93. if the breaker is manually closed on to a fault condition it will thus be free to trip and will again lock open.

The mechanism also includes an inertia device com- ,1 .om-g in this embodiment an anvil member 111 carried by an arm 112 mounted on a fixed pivot 113, and cooperating with a fixed stop 112m an abutment surface 11d of the anvil being engaged by the switch lever 22 during the upward movement of the latter as the latter approaches the contact open position. The surface 114 may be provided by a plunger slidably mounted in the anvil with a compression spring 111i2L (Fig. 2) interposed between said plunger and the anvil. The kinetic energy in the moving parts is thus transferred to the pivoted anvil 111 causing rapid retardation of said moving parts. The anvil moves upwardly into engagement with a suitable butter 115 whereby to absorb said energy. An additional butl'er 116, of suitable construction, is mounted on the frame for nally arresting the upward movement of the contact rod by engagement with the upper end of the link 17.

1t will be understood that certain of the links and springs described may be of duplicated construction for convenience in mounting and assembly, such duplicated construction being apparent in Figs. 2 and 3 in the case of some of the links.

A preferred construction of dashpot is illustrated by Fig. 4 wherein the control valve operated by the cam '70 and lever 69 is of the poppet or mushroom type comprising a head carried by a stem 121 and co-operating with a seat formed by a diaphragm 122 held in place by an end member 123. The valve is guided by means of a further diaphragm 124 through which the stem 121 extends, and a diaphragm 125 above the valve mounted at the base of the dashpot cylinder, and having a central perforation through which a spigot rod 126 mounted in the valve stem 121, extends. The valve is urged downwardly from its illustrated position into engagement with its seat 122 by means of a compression spring 127. The valve is maintained lifted by a pivoted rocker 128 engaged by a crankarm 129 made fast to the shaft 69 so that the movement of the cam 70 causing clockwise movement of the arm 68 in Fig. l (counterclockwise movement of said arm in Fig. 4) will allow the spring 127 to close the valve. Openings such as appearing at 130 are provided in the diaphragms 124 and 125 for allowing free passage of oil from the dashpot when the valve is opened.

When the valve is closed, only a slow discharge of oil from beneath the piston shown at 66 is permitted by a bleed discharge port 131 which preferably comprises a removable perforated plug 132. By this means various rates of movement may be obtained by selection of plugs 132 having different sizes of orifices therein.

The upper end of the dashpot cylinder 65 is in communication with the tank by means of a bleed discharge port 133 preferably comprising a removable bored metering plug 134 whereby again to provide ready control of the rate of movement of the piston 66a upwardly during the re-closing stroke. In order that the downward or opening stroke of the dashpot shall be controlled independently of the port 133 the upper end of the dashpot cylinder is closed by a cylinder cover 135 having ports of which two appear at 136 and a disc valve 137 is urged into engagement with the underside of said cover by means of a compression spring 138. This valve therefore closes the ports 136 during upward movement of the piston 66l but during downward movement of the latter the disc 137 will move downwardly to allow passage of oil through said ports and a central opening 139 in the disc valve 137.

It will be understood that at all times when the rack is raised from the illustrated position it tends to return at a relatively low speed to the illustrated position under control of the clockwork device 88 so that after ea-ch occasion on which over-current conditions occur, except when the contacts are locked open, the mechanism returns automatically to the illustrated condition in readiness for a further cycle of operations above described in response to a subsequent occurrence of over-current conditions.

While we have shown and described a particular embodiment of our invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from our invention in its broader aspects and we, therefore, intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In a circuit breaker having a switch member movable between a closed position and an open position, an

overcenter toggle linkage operatively coupled to said movable switch member, an overcenter spring urging said toggle linkage into a first collapsed position wherein said switch member is in closed position, actuating means for driving said toggle toward center to charge said overcenter spring and for thereafter driving said toggle past center to permit said charged spring to urge said toggle toward a second collapsed position wherein said switch member is in open position, abutment means operable when interfering with said toggle to render collapsing movement thereof ineffective to produce opening movement of said switch member, said abutment means being disposed to interfere with said toggle during movement thereof through and initially past center whereby to preclude opening movement of said switch member during this interference interval, said toggle being movable out of interfering relationship with said abutment means upon continued movement of said toggle past center whereby then to permit said spring quickly to drive said toggle into said second collapsed position, thus driving said switch member into open position.

2. The combination of claim 1 wherein said toggle linkage is returnable from said second to said first collapsed position to return said switch member to closed position, said abutment means temporarily interfering with return movement of said toggle and permitting said overcenter spring to initiate closing movement of said switch member only after said toggle has been returned a substantial distance past toggle center.

3. The circuit breaker mechanism of claim l in combination with timing means for limiting the speed of said actuating means to a rate which is substantially less than the opening speed of said movable switch member.

4. The circuit breaker of claim 2 in combination with reclosing means operable following opening of said contact to return said toggle from said second to said rst collapsed position, timing means for limiting the speed of operation of said reclosing means and of said actuating means to rates which are substantially lower than the closing and opening speeds, respectively, of said switch member.

5. In a circuit 'breaker having a switch member movable between a closed position and an open position, an overcenter toggle linkage operatively coupled to said movable switch member, an overcenter spring urging said toggle linkage into a first collapsed position wherein said switch member is in closed position, actuating means for driving said toggle towar-d center to charge said overcenter spring and for thereafter driving said toggle past center to permit said charged spring to urge said toggle toward a second collapsed position wherein said switch member is in open position, abutment means operable when engaging a predetermined portion of said toggle to render collapsing movement of said toggle ineffective to produce opening movement of said switch member, said predetermined toggle portion being engageable with said abutment means as the toggle is moved through center and for an initial distance past center whereby to preclude opening movement of said switch member during this interference interval, said predetermined toggle portion being disengageable from said abutment means upon continued movement of said toggle past center, whereby then to permit said spring quickly to drive said toggle into said second collapsed position, thus driving said switch member into open position.

6. In a circuit breaker having a Contact movable between a closed position and an open position, an overcenter toggle linkage operatively coupled to said movable contact, an overcenter spring urging said toggle linkage into a first collapsed position on one side of toggle center, actuating means for driving said toggle toward center to charge said overcenter spring and for thereafter driving said toggle past center to permit said charged spring to urge said toggle toward a second collapsed position, means interconnecting said toggle and said contact for positioning said contact in a closed position when said toggle is in said rst collapsed position and responsive to movement of said toggle into said second collapsed position to drive said contact into open position, abutment means operable when interfering with said toggle to render movement thereof past center ineffective to produce opening movement of said contact, said abutment means being disposed to interfere with said toggle during movement thereof through and initially past center whereby to preclude opening movement of said contact during this interference interval, said toggle being movable out of interfering relationship with said abutment means upon continued movement of said toggle past center whereby then to permit said spring quickly to drive said toggle into said second collapsed position, thus producing movement of said contact into open position.

7. In a circuit breaker having a contact movable between a closed position and an open position, an overcenter toggle linkage operatively coupled to said movable contact, an overcenter spring urging said toggle linkage into a first collapsed position wherein said contact is in closed position, actuating means for driving said toggle toward center to charge said overcenter spring and for thereafter driving said toggle past center to permit said charged spring to urge said togggle toward a second collapsed position wherein said contact is in open position, interference means operable during movement of said toggle through center and initially past center for precluding opening movement of said contact, and means for rendering said interference means inoperable to preclude said Contact opening movement upon continued movement of said toggle past center whereby then to permit said overcenter spring quickly to drive said toggle into said second collapsed position, thus producing movement of said contact into open position.

8. The combination of claim 7 wherein said toggle linkage is returnable from said second to said first collapsed position to return said contact to closed position, said abutment means temporarily interfering with return movement of said toggle and permitting said overcenter spring to initiate closing movement of said contact only after said toggle has been returned a substantial distance past toggle center.

9. The circuit breaker mechanism of claim 7 `in combination with accelerating means including a chargeable accelerating spring which upon discharge acts to drive said contact toward open position, charging means operated by said actuating means during movement of said toggle toward, through and initially past center for progressively charging said accelerating spring, means for applying the stored energy of said accelerating spring to a portion of said ymechanism which is under the control of said interference means, said interference means thereby preventing discharge of said accelerating spring until rendered inoperable whereupon said accelerating spring then discharges and aids said overcenter spring in driving said contact open.

10. In a circuit breaker having a contact movable between a pair of spaced-apart circuit-controlling positions, an overcenter toggle linkage operatively coupled to said movable contact, an overcenter spring urging said toggle linkage into a first collapsed position wherein said contact is in one of its circuit-controlling positions, actuating means for driving said toggle toward center lto charge said overcenter spring and for there-after driving said toggle past center to permit said charged spring to urge said toggle toward a second collapsed position wherein said contact is in the other of its circuit-controlling positions, abutment means operable when interfering with said toggle to render movement thereof past center ineffective to produce movement of said contact between said circuit-controlling positions, said abutment means being disposed to -interfere with said toggle during movement thereof through and initially past center whereby to preclude circuit-controlling movement of said contact during this interval, said toggle being movable out of interfering relationship with said abutment means upon continued movement of said toggle past center whereby then to permit said spring quickly to drive said toggle into said second collapsed position, thus producing movement of said contact into said other circuit-controlling position.

11. The combination of claim 10 wherein said toggle linkage is returnable from said second to said first collapsed position to return said contact to said one circuitcontrolling position, said abutment means temporarily interfering with return movement of said toggle and permitting said overcenter spring to initiate return motion of said contact only after said toggle has been lreturned a substantial distance past toggle center.

12. In a circuit breaker having a contact movable between a pair of spaced-apart circuit-controlling positions, an overcenter toggle linkage coupled to said movable contact, an overcenter spring urging said toggle linkage into `a first collapsed position wherein said toggle is in one of said circuit-controlling positions, actuating means for driving said toggle toward center to charge said overcenter spring and for thereafter driving said toggle past center to permit said charged spring -to urge said toggle toward a second collapsed position wherein said contact is in the other of said circuit-controlling positions, interference means operable during movement of said toggle through center and initially past center for precluding opening movement of said contact, and means for rendering said interference means inoperable to preclude said circuit-controlling movement upon continued movement of said toggle past center, whereby then to permit said spring quickly to drive said toggle into said second collapsed position, thus producing movement of said contact into said other circuit controlling positions.

13. In a circuit breaker having a contact movable between a pair of spaced-apart circuit-controlling positions, an over-center toggle linkage comprising a pair of toggle links one of which is a tioating link coupled to said movable contact, an overcenter spring urging said toggle linkage into a first collapsed position wherein said contact is in one of said circuit-controlling positions, actuating means coupled to the other of said toggle links and operable to drive said toggle toward center to charge said overcenter spring and for thereafter driving said toggle past center to permit said charged spring to urge said toggle toward a second collapsed position wherein said contact is in the other of said circuit-controlling positions, abutment means operable when interfering with said floating link to render collapsing movement of said toggle ineffective to produce circuit-controlling movement of said contact, said abutment means being disposed to interfere with said iioating link during movement of said toggle through and initially past center whereby to preclude circuit-controlling movement of said contact during this interval, said oating link being movable out of interfering relationship with said abutment means in rcsponse to continued movement of said toggle past center whereby then to permit said spring quickly to drive said ltoggle into said second collapsed position, thus producing movement of said contact into said other circuit-controlling position.

14. The circuit breaker mechanism of claim 13 in rcombination with accelerating means including a chargeable accelerating spring which upon discharge acts to drive said contact toward said other circuit-controlling position, charging means operated `by said actuating means during movement of said toggle through and initially past center for progressively charging said accelerating spring, means for applying the stored energy of said accelerating spring to a portion of said mechanism which is under the control of said interference means, said interference means thereby preventing discharge `of said accelerating spring until rendered inoperable whereupon said accelerating spring then discharges and aids said overcenter spring in producing movement of said Contact toward said other circuit-controlling position.

References Cited in the file of this patent UNITED STATES PATENTS 1,031,479 Smith July 2, 1912 1,721,417 Schwennker July 16, 1929 1,810,624 Rankin June 16, 1931 1,848,902 Paxton et al. Mar. 8, 1932 2,542,736 Viti et al Feb. 20, 1951 

